1. Field of Invention
The present invention relates to new polymers containing laterally substituted isocyanate groups and their preparation and particularly to polymers prepared from acyl azide monomers.
2. Description of Prior Art
Although the chemistry of isocyanates was studied extensively towards the end of the last century, interest in their technology started only in the last forty years, when the di- and trifunctional isocyanates began to be applied to the synthesis of various polymeric products.
The more important known reactions of the isocyanate groups, those with compounds containing one active hydrogen group are: ##STR1##
Generally, these reactions take place readily even at room temperature upon merely mixing the reagents. Compounds containing two or more substituents with active hydrogen groups similarly react with bi-functional or polyfunctional isocyanates to produce a great variety of polymers. The most important group of such products are the polyurethanes, known to the art as the reaction products from di- or polyols with di- or polyisocyanates and are defined as those containing the characteristic group ##STR2## These polymers have different uses and applications such as plastic fibers, elastomers, adhesives, coatings, etc.
It is particularly desirable to synthesize polymers which possess various proportions of isocyanate groups laterally substituted on the main chain. Such polymers can be easily modified, by grafting or crosslinking reaction between the isocyanate groups and compounds containing active hydrogen groups. Another possibility is the reaction between two isocyanate groups, which results in the formation of a four-membered ring known as an uretidenedione. Homopolymers and copolymers of vinyl monomers containing isocyanate groups, are known to the art. Some typical examples are as follows: U.S. Pat. No. 2,606,892 describes copolymers of propenyl isocyanate with methyl acrylate. The copolymers obtained are claimed to impart special properties to textiles and to be useful as binders for various fillers. In the Japanese Pat. No. 5145 (1958)--see Chemical Abstracts 53, 10846 (1959)--a copolymer of isopropenylisocyanate with acrylonitrile is described for which better dyeing properties than these of the homopolyacrylonitrile are claimed. A recent article--J. Macromolecular Sci.--Chem. A5, (6), 1063 (1971) describes copolymers of vinyl isocyanate with styrene, methyl acrylate and fumaronitrile also mentioning some of their properties and their reactions with alcohols and amines.
The main problem rendering difficult the preparation of these isocyanates and their subsequent homopolymerization or copolymerization, is the usually great sensitivity of the isocyanate group to moisture. Particular caution in handling monomers containing isocyanates, and especially perfectly dry conditions, are required in carrying out their polymerization. Other disadvantages attendant on the utilization of isocyanate-containing vinyl monomers are their toxicity and their relatively short shelf-life due to their tendency to dimerize or trimerize.